This invention relates to an image-receiving element for use in photographic film units of the diffusion transfer type. More particularly, the invention relates to an image-receiving element especially adapted for use in diffusion transfer photographic film units of the type wherein an image-receiving element is designed to be separated from a photosensitive element after exposure and photographic processing have been effected.
Photographic film units of the diffusion transfer type, including those of the aforementioned "peel-apart" type, are well known in the art and have been described in numerous patents. Exemplary of these are U.S. Pat. Nos. 2,983,606; 3,345,163; 3,362,819; 3,594,164; and 3,594,165. In general, diffusion transfer photographic products and processes involve film units having a photosensitive system including at least one silver halide layer, usually integrated with an image-providing material, e.g., an image dye-providing material. After photoexposure, the photosensitive system is developed, generally by uniformly distributing an aqueous alkaline processing composition over the photoexposed element, to establish an imagewise distribution of a diffusible image-providing material. The image-providing material is selectively transferred, at least in part, by diffusion to an image-receiving layer or element positioned in a superposed relationship with the developed photosensitive element and capable of mordanting or otherwise fixing the image-providing material. The image-receiving layer retains the transferred image for viewing. In diffusion transfer photographic products of the so-called "peel-apart" type, the image is viewed in the image-receiving layer upon separation of the image-receiving element from the photosensitive element after a suitable imbibition period. In other products, such separation is not required.
Image-receiving elements particularly adapted for use in "peel-apart" diffusion transfer film units have typically embodied an image-receiving layer for retaining the transferred image arranged on a substrate layer of suitable material or a combination of layers arranged on the substrate layer, each of the layers providing specific and desired functions adapted to the formation of the desired photographic image in accordance with diffusion transfer processing. Thus, in one well known embodiment the image-receiving element typically comprises a support material (preferably, an opaque support material carrying a light-reflecting layer for the viewing of the desired transfer image thereagainst by reflection); a polymeric acid-reacting (neutralizing) layer adapted to lower the environmental pH of the film unit subsequent to substantial transfer image formation; a spacer or timing layer adapted to slow the diffusion of the alkali of an aqueous alkaline processing composition toward the polymeric neutralizing layer; and an image-receiving layer to receive the transferred photographic image. Such preferred structure is described, for example, in the aforementioned U.S. Pat. No. 3,362,819 and is illustrated in other patents, including U.S. Pat. Nos. 4,322,489 and 4,547,451.
It is known in the art to utilize a stripping layer in such image-receiving elements to facilitate the separation of the image-receiving layer from the photosensitive element after photographic processing. U.S. Pat. No. 4,009,031 discloses and claims an image-receiving element of this type wherein the stripping layer is formed by coating the image-receiving layer with an aqueous solution of a hydrophilic colloid, such as gum arabic, and ammonia. Such stripping layers have proved to be very effective for their intended purpose. However, in some instances, particularly when the image-receiving element and photosensitive element are peeled-apart relatively slowly, striations may occur on the surface of the image-receiving element. These are thought to be due to some of the stripping layer material remaining on the image-receiving layer after separation and may adversely affect the desired quality of the photograph.
It would be very desirable to provide image-receiving elements wherein such striations can be significantly reduced or eliminated.